未释磷及释磷污泥生物炭内源磷释放特征及影响因素研究

Characterization of endogenous phosphorus release from nonphosphorus-releasing and phosphorusreleasing sludge biochar:key influencing factors on phosphorus release behavior

在市政污泥制备生物炭并作为水处理吸附剂的过程中,富含磷(P)的污泥释放出的磷有可能引发环境二次污染,这是亟须关注的环境问题。研究以污泥生物炭(Biochar,BC)和低温热处理(Low Temperature Phosphate Release Biochar,RC)、酸碱(Acid and Alkali Phosphate Release Biochar,AB)、热酸解(Thermal Acid Phosphate Release Biochar,PBC)释磷污泥生物炭为研究对象,考察不同释磷技术对污泥中磷释放的影响,通过对比释磷和未释磷污泥生物炭在水中的释放行为,揭示了影响内源磷释放的环境因子。研究结果显示:热酸解技术对污泥释磷效果最好,最佳释磷率达55.40%;污泥中磷主要以无机磷(Inorganic Phosphorus,IP)的形态存在;经过预释磷处理的污泥生物炭在水体中的累积释放质量比显著低于未释磷污泥生物炭;不同处理污泥生物炭磷的累积释放质量比由大到小依次为PBC、RC、AB、BC;生物炭内源磷释放符合拟二级动力学模型,表明生物炭的磷释放是化学过程。环境条件对污泥生物炭的释磷影响为:在酸性条件、较高固液比(g∶m L)、部分阴离子(Cl^(-)、SO_(4)^(2-)、NO_(3)^(-))和阳离子(Na^(+)、K^(+))可促进BC、RC和AB中磷的释放,Ca^(2+)抑制磷释放,但是环境条件对PBC中磷的释放影响不大,表明PBC在不同环境条件下的应用更具有安全性和稳定性。研究将对污泥生物炭的安全性应用提供理论和技术支撑。

In this study,we focused on sludge Biochar (BC)and phosphorus-releasing sludge biochar subjected to Low Temperature Phosphate Release Biochar (RC),Acid and Alkali Phosphate Release Biochar (AB),and Thermal Acid Phosphate Release Biochar (PBC).We examined the effects of various phosphorus release methods on phosphorus liberation from sludge.By comparing the release patterns of phosphorusreleasing and non-phosphorus-releasing sludge biochar in water,we identified the environmental factors influencing endogenous phosphorus release.The study results indicated that lowtemperature heat treatment,acid-base treatment,and thermal acidolysis achieved the highest phosphorus release rates from sludge,at 48.5%,33.9%,and 55.4%,respectively.Among these methods,thermal acidolysis had the most pronounced effect on phosphorus release,with optimal conditions established at 50℃and p H=3.The analysis of phosphorus release patterns in sludge from various treatment groups revealed that phosphorus was primarily released in the form of Inorganic Phosphorus (IP),with the Non-Available Inorganic Phosphorus (NAIP) pattern being the most dominant among the IP categories.The percentage of NAIP released from the different treatment groups exceeded 47%.The cumulative mass ratio of phosphorus released into the water column was significantly lower for sludge biochar subjected to pre-phosphorus release treatment compared to that of sludge biochar without phosphorus release.The cumulative mass ratios of phosphorus released from the various treated sludge biochar followed this descending order:PBC,RC,AB,and BC.Notably,the cumulative mass ratio of phosphorus released from PBC-treated sludge biochar was significantly lower than that from the BC group,decreasing from 48.48 mg/g(BC) to 10.46 mg/g (PBC).Endogenous phosphorus release from biochar aligns with the proposed secondary kinetic model,suggesting that phosphorus release is a chemical process.The influence of environmental conditions on phosphorus release from sludge biochar is summarized as follows:under acidic conditions and at higher solid-to-liquid ratios (g:m L),anions (Cl~-,SO_4~(2-),NO_3~-) and cations (Na~+,K~+) significantly enhanced phosphorus release from BC,RC,and AB.However,Ca~(2+)inhibited phosphorus release.Environmental conditions had minimal impact on phosphorus release from PBC.To mitigate the risk of phosphorus release from sludge biochar,pretreating the sludge through thermal acid digestion is a more effective technological approach.